At present, it is customary for a control circuit for a lift to be accommodated on a printed-circuit board. The center of that circuit is a control element, typically a microprocessor, controller or the like. The control element controls the functions of the lift and the associated aids, more specifically the lift motor which lifts or lowers the lift, and the lift doors. To that end, the control element processes a large number of operating signals which are presented on respective inputs of the control element, and which originate from respective switches. The term "switch" in this connection is given a broad interpretation, and is understood to include, inter alia, all control buttons in the lift cabin, all control buttons on the various floors, all safety detectors such as door closing switches and cabin position detectors.
The switches are typically of the "make contact" or "break contact" type, i.e., the switches typically have two switch contacts, and they can typically be in two switch states, viz. a first switch state, in which the electrical resistance between those switch contacts is substantially infinite (open switch state), and a second switch state, in which the electrical resistance between those switch contacts is very low (closed switch state).
On the printed-circuit board, terminals are provided, to which the switch contacts of the switches mentioned can be connected by, electrical lines. Those terminals are connected by print tracks to a voltage source and the inputs of the control element. A risk associated with print tracks is their becoming defective; more particularly, there is the danger of short-circuiting between two print tracks, which may cause an operating Eignal to end up at a wrong input of the control element, so that the reactions of the control element no longer correspond with the instructions given by the control buttons and/or the conditions detected by the safety detectors. It will be clear that this may cause fatally dangerous situations.
To reduce these risks, the mutual distances between the print tracks on the printed-circuit board are selected to be fairly great, typically in the order of 4 mm. As a consequence, however, the spatial dimensions of the printed-circuit board have to be rather great. Further, by such an approach, the risks referred to cannot be reduced adjacent the control element proper, because there the mutual distances between the print tracks are determined by the mutual distances between the terminal pins of the control element (IC).